1. Field of the Invention
The present invention relates to an image forming apparatus for reading an image depicted on an original to print it on a sheet, and a method for controlling the image forming apparatus.
2. Description of the Related Art
An image forming apparatus such as a copy machine optically reads an image on an original set on an original table, forms an electrostatic latent image corresponding to the read image on the surface of a photosensitive drum, and develops (visualizes) the electrostatic latent image with a developing agent (toner) to print (transmit) it on a paper-sheet. The formation of the electrostatic latent image on the photosensitive drum is performed by scanning with a laser beam radiated from a semiconductor laser, for example, a laser diode.
The scanning with the laser beam is linearly performed along the axial direction of the photosensitive drum. The linear scanning is referred to as primary scanning. The primary scanning is repeatedly performed by rotation of the photosensitive drum. Sequential movement of the primary scanning by the rotation of the photosensitive drum is referred to as secondary scanning.
The image read from the original is composed of a number of picture elements. The primary scanning and the secondary scanning are performed by “on” and “off” the laser beam in accordance with these picture elements.
The actual “on” and “off” of the laser beam are performed in accordance with each picture element in one case, or in accordance with plural divided portions, for example, 4 divided portions of each picture element in another case. By the “on” and “off” in accordance with each divided picture element, edge portions of the read images can be reproduced in detail on the sheet. This is a so-called multi-segment smoothing process.
On the other hand, the developing agent (toner) for developing the electrostatic latent image on the photosensitive drum is consumable, and it much be replenished regularly or when needed. For this replenishment, a user is burdened with a fee. The consumption of the developing agent, which burden the user with the fee, is an important concern to the user.
Conventionally, the consumption fee of the developing agent is calculated on the basis of the number of the used paper-sheets at a store or a rental store of the apparatus. The thus calculated consumption fee is demanded of the user.
The amount of the images to be printed on the sheets varies, and it cannot be accurately grasped only from the number of the used paper-sheets. Therefore, there is possibility that an improper fee is demanded of the user.